Fan arrangement having automatic control capability

ABSTRACT

A fan arrangement with a motor for rotating the impeller thereof. A signal generator for producing an electrical signal in accordance with the rotational speed of the impeller. The generator including a stationary claim-pole unit with a pickup member. The rotor including a multi-pole permanently magnetized ring positioned outwardly of the claw-pole unit has been inserted.

United States Patent [1 1 Papst et al.

[ June 26, 1973 FAN ARRANGEMENT HAVING AUTOMATIC CONTROL CAPABILITY [75]Inventors: Georg F. Papst; Hans-Dieter Papst,

both of Georgen, Germany [73] Assignee: Papst-Motoren KG, Georgen,

Germany [22] Filed: Sept. 23, 1970 [21] Appl. No.: 74,604

[30] Foreign Application Priority Data Sept. 27, 1969 Germany P 19 48906.6

[52] U.S. Cl 310/67, 310/62, 310/168 [51] Int. Cl. H02k 7/00 [58] Fieldof Search 310/67, 62, 63,171, 310/68, 68 E, 263,113,114, 257,168,169,

[56] References Cited UNITED STATES PATENTS 3,596,122 7/1971 Stewart310/67 3,509,395 4/1970 Schrccongost 310/168 2,467,582 4/1949 Corkran318/463 3,504,208 3/1970 Rivers 310/257 2,926,838 3/1960 Van Rijn2,990,112 6/1961 Levy 310/67 2,206,920 7/1940 Riggs 310/171 UX 2,829,2874/1958 Font 310/67 3,486,054 12/1969 Livingston 310/171 3,553,557 1/1971Korthaus 318/463 3,538,362 11/1970 Cheetham 310/171 FOREIGN PATENTS ORAPPLICATIONS 975,641 11/1964 Great Britain 310/168 897,190 3/1945 France310/169 Primary Examiner--R. Skudy Attorney-Michael S. Striker [57]ABSTRACT A fan arrangement with a motor for rotating the impellerthereof. A signal generator for producing an electrical signal inaccordance with the rotational speed of the impeller. The generatorincluding a stationary claimpole unit with a pickup member. The rotorincluding a multi-pole permanently magnetized ring positioned outwardlyof the claw-pole unit.

4 Claims, 11 Drawing Figures PATENTEDJUN 2 6 I973 SHEET 1 OF 2 lnventors: (Fen/u F- P0 PJT men-"1 AqPsT' Fig}; Z7 28 293022 2 AttorneysFAN ARRANGEMENT HAVING AUTOMATIC CONTROL CAPABILITY BACKGROUND OF THEINVENTION Small fans are used for the cooling and ventilationrespectively of electronic devices, computer units and so on. In specialcases the reliability of the ventilation of such electronic devices canbe of extraordinary importance and therefore requires supervision. Thereare also other applications of small electric motor driven fans whereany irregularity in the number of rotations of the electric motorrequires immediate attention and where a protection device in accordancewith the invention can be applied.

Known thermal protection elements can be used for the above purposes insome such cases, such elements responding, when the rotor is not inmotion due to overheating, at a given excess temperature, for instance120 percent of the nominal working temperature, and which are on sale inquality tolerance classes of for instance i 3 percent (these are veryexpensive); i 6 percent; 10 percent. However, these are unreliable owingto the time lapse before these responding values are reached. Besides,thermal elements do not for example not respond if the fan stops upon asupply failure. Furthermore, especially with small fans and fan motors,the power input at nominal performance while running, and at shortcircuit (with stopped rotor), does not show sufficient difference inmost instances to be used for reliable protective measures.

There are also known for safeguarding electronic devices air currentpressure switches or so-called wind switches which respond when the aircurrent pressure in a ventilated electronic chamber ceases. However, asthe air current conditions can be very different in a device due todifferences in mounting, to different makes of fans, and also todifferent positioning of the current pressure switching elements in thehousing and because it is wished to switch off the cooled device as soonas possible when a fan has ceased difficulties result in practice.

An object of the present invention is to find a device which can causeimmediate, reliable and simple safety precautions when a fan has ceased,at the same time avoiding thedisadvantages described above.

In accordance with the invention, there is provided a protection device,particularly for small fans, charac' terized in that a voltage createdby a tacho-generator known per se is used to protect the motor or otherdevices to be cooled, whose number of rotations is dependent on thenumber of rotations of the fan.

In such a protection device it is advantageous if the fan includes acentral shaft which rotates in a stationary bearing, and thetacho-generator comprises a polarized magnetic ring mounted on the shaftand a winding encircling the shaft.

It is furthermore advantageous according to the invention if the fanarrangement includes switching means responsive to the output voltage ofthe tachometer generator for disconnecting a load coded by said fanarrangement when said voltage falls below a predetermined value. In somecases it is advantageous if said winding is provided in the stator of amotor driving the fan.

In a preferred embodiment of the invention, the fan has blades offerromagnetic material and includes a housing surrounding the fanblades, and a magnetic field sensitive induction element is provided inthe fan housing to form with the fan blades a tacho-generator.

Naturally, it will be appreciated that many variations may be effectedwithout departing from the spirit and scope of the present inventiveconcept.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing inwhich corresponding parts have been given the same reference numerals.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 comprises sectional elevationsof two types of combined motor and tacho-generator used in theinvention, the right-hand part of the figure showing one embodiment andthe left-hand the other;

FIG. 2 is a section along a radius of a combined fan andtacho-generator;

FIG. 3 is a side view of the apparatus of FIG. 2, partly sectioned asindicated on FIG. 2',

FIG. 4 is a sectional elevation of a further combined motor andtacho-generator;

FIG. 5 illustrates in section a tacho-generator attached to the flangeof a fan driving motor;

FIGS. 6 and 7 illustrate diagrammatically modifications of the apparatusof FIG. 5;

FIG. 8 illustrates, partly diagrammatically and partly in section, afinal form of combined motor and tachogenerator;

FIG. 9 is a side view corresponding to FIG. 8, partly .sectioned asindicated in FIG. 8;

FIG. 10 illustrates a system embodying the invention in which any of theapparatus shown in the above figures may be used; and

FIG. 10a illustrates an alternative component for use in the system ofFIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tacho-generators of FIGS.1, 5 to 7, 8 and 9 are of the claw pole type, whereas those of FIGS. 2and 3 have individual ring magnets.

FIG. 1 illustrates in section an axial fan with an external cage rotor1, a rotor hub or shaft bush 2, a shaft 3 carrying, in the left-handembodiment, via a nonmagnetic intermediate member 4 made for example ofbrass, a permanent magnet ring 5 intermittently polarized around itscircumference so as to form an arrangement of poles, said ring inducinga voltage proportional to the speed of rotation in a claw polearrangement 7 having an output winding 6. This arrangement is intendedprimarily for a motor having a three-phase cur rent winding with thewinding distributed over the whole circumference without interruption.

The right-hand half of the cross-section shown in FIG. 1 illustrates atacho-generator with an axial air gap, in which the ring 5 is magnetizedat its side 9, facing an inductive air gap 8, with intermittent polesand serving to induce a voltage in the winding 11 of a claw polearrangement 10 proportional to the speed of rotation. In thisembodiment, the generator lead 12 is led out through a gap in the motorwinding together with the motor winding lead 13; in this case the motorwinding could be, for example, a split pole winding with distinct poles.

Similar arrangements can be used with internal rotor motors.

FIG. 2 and 3 show part of a fan whose impeller means, here in the formof blades 117, are of ferromagnetic material. An induction element 14 ismounted in the housing T8 of the fan. The induction element l4 comprisesa permanent magnet having poles 119, 2b joined by a section which issurrounded by the output coil 6. The passage of each fan blade I! lowersthe reluctance of the magnetic circuit of the magnet 15 and a sequenceof unidirectional voltage pulses is thus induced in the coil 6; theaverage output voltage is thus dependent on the speed of rotation of thefan. The element 114 is arranged so that the poles 119, 26) lie in aline parallel to the edge of the fan blade I7 as it passes to give themaximum inductive change. It is necessary only to have two openings inthe housing I8, for the insertion of the poles 119, 20.

As best seen in FIG. 3, the induction element 114 may be encased in asynthetic material for assembly onto the fan as a unit, for instance ina casing 114'.

In special cases one can arrange for two induction units facing eachother, or several induction units symmetrically distributed, especiallyfor reasons of equalizing the eccentricity of the fan wheel, by suitablecircuitry.

FIG. 4 illustrates an external rotor motor in which,

for reasons of weight distribution, ferromagnetic parts 211 or permanentmagnetic parts 22 are arranged on the open end of the rotor housingbell, and are distributed evenly over the circumference, protruding inan axial direction. The moving said parts induce a voltage in inductioncoils 23 in the axially opposite portion 25 of a flange 24, theseportions carrying permanent magnetic cores 311 or soft iron magneticcores 32. The upper half of the cross-section illustrates an embodimentwith an eddy current rotor housing 26; the lower half illustrates thesame with a cage housing 27 having a packet of iron laminae 28. Thetacho-generating parts 22 are attached, for instance by being pressedinto a cast-in groove 341) in an end ring 29.

FIG. 5 illustrates as one embodiment an attachment unit comprising anexternal tacho-generator 33 mounted on the side of a flange 24, wherethe shaft 3 protrudes. The tacho-generator attachment 33 with winding 6and claw poles 7 is held in a simple manner by fitting into the housing,by means of radially resilient enlarged portions 35 individuallyprotruding in an axial direction, with noses 36 which penetrate intocorresponding depressions 38 provided in a rim 37 on the flange 24. Themagnetic pole wheel 5 is adjusted by means of a gauge into the rightaxial position towards the inducting system and then secured, forexample by gluing, which also overcomes even very unfavorable adding ofaxial tolerances in the stator in a simple manner.

It will be apparent that such a tacho-generator can be added to anexisting motor.

In FIG. 6, as a variation of FIG. 5, the rim 37 has been pulled insidetowards the side of the motor, in Order to avoid protruding of any partsof the exterior surface of the flange.

FIG. 7 illustrates a variation of the. mounting of FIG.

' 5, having an elevated edge ldl forming one piece with the flange 24,into which again the same exterior tachogenerator 5 to 7 has beeninserted, which is closed by a simple flat cover 4-1. The depth of thisedge 24 depends on the axial length of the tacho-generator to beinserted.

FIG. 8 and 9 illustrate a portions of an outer rotor 28, 29 with amulti-pole magnetized ring 45 in cooperation with a stationary claw poleunit 46, 47 enclosed by said ring (compare 6, '7 in FIG. ii). In thisembodiment, an annular ferromagnetic member 48 is arranged to protrudeover the open rotor housing edge,

.to allow the magnetic ring 45 to be inserted into the protrudingportion of the ring 48 which serves at the same time as a magneticreturn circuit member of the claw pole unit 47, that is, of clawportions 47a and 47b. The claw portions 47a, 47b are most clearly seenin FIG. 9. From FIG. 9 it will be clearly seen that claw pole unit 47comprises a first group of claw portions 417a and a second group of clawportions 47b axially spaced from the first group and defining therewitha circumferential recess accommodating pick-up winding means 46. Thegenerator winding 46 is situated in the claw pole ring which, in thisembodiment, is fixed to the flange 2d.

The claw pole body 47 with the claws 47a, 47bencircles the electricalwire circular winding 46 inserted therein, and the multipole magnet ring45 works in conjunction therewith via the air gap 49. In the practicalembodiment this magnet ring 45 is a flexible permanent magnet strip,lying against a wedge 50 adjoining the ring 48; this is known, forexample, by its trade name Sprox. This flexible permanent magnet hasbeen magnetized beforehand with a high current load (current impact of10 to 10 Amp.) over an inflexible meander-shaped conductor, whoseconductor distances correspond to the distribution of claws of the clawpoles.

FIG. 10 illustrates the working of monitoring means according to theinvention. With any drop in the number of rotations of the motor (M) 52the tachogenerator (G) 54 mechanically connected thereto (as indicatedby numeral 53) gives off a reduced induced voltage over a two-phase lead55, to an amplifier 56, whose output a7 is connected to a low tensionswitch 58, or the equivalent, which interrupts the two-or three-phasesupply 59 to the motor when the value of the voltage is less than areference value. This interruption of the motor lead 59, however, mustnot take place when starting the motor by means of switch 60, when thegenerator, being still in its static state, cannot yet supply anyvoltage. For this reason, a time-delay relay (Ella, which works togetherwith the motor switch 60, only opens the bridging member 62 when themotor switch 60 has remained closed for a certain time. Mb in FIG. aindicates a thermal variant of starter relay 61a.

While tacho-generators are known for other control purposes, theinvention achieves a simple, space-saving control protection requiringno extra mounting, which overcomes the disadvantages described in theintroduction of known protection devices for electronic fans andventilation devices.

Many possible modifications will become apparent from the foregoingwithout departing from the spirit of the present invention. However, theforegoing disclosure is presented in an illustrative sense rather than alimiting sense and the appended claims are relied upon to define thescope of the present invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

We claim:

1. A fan arrangement having automatic control capability comprisingrotatable impeller means; motor means for rotating said impeller meansand including external rotor means; and signal-generating means forgenerating an electrical signal which is a function of and indicative ofthe rotational speed of said impeller means, said signal-generatingmeans comprising a stationary claw pole unit including pick-up windingmeans, and a multi-pole permanently magnetized ring comprising aflexible permanently magnet strip radially outwardly of said claw-poleunit and being mounted on and rotatable with said rotor means relativeto said claw pole unit.

2. A fan arrangement as defined in claim 1, said external rotor meanscomprising an annular ferromagnetic member radially outwardly of andsurrounding said magnetized ring.

3. A fan arrangement as defined in claim 2, said claw pole unitcomprising a plurality of radially outwardly projecting claw portions.

4. A fan arrangement as defined in claim 2, said claw pole unitcomprising first and second groups of axially spaced peripherally offsetradially outwardly projecting claw portions together defining acircumferential recess, and said pick-up winding means comprisingelectrical wire means coiled around said claw pole unit and accommodatedin said circumferential recess.

1. A fan arrangement having automatic control capability comprisingrotatable impeller means; motor means for rotating said impeller meansand including external rotor means; and signal-generating means forgenerating an electrical signal which is a function of and indicative ofthe rotational speed of said impeller means, said signal-generatingmeans comprising a stationary claw pole unit including pick-up windingmeans, and a multi-pole permanently magnetized ring comprising aflexible permanently magnet strip radially outwardly of said claw-poleunit and being mounted on and rotatable with said rotor means relativeto said claw pole unit.
 2. A fan arrangement as defined in claim 1, saidexternal rotor means comprising an annular ferromagnetic member radiallyoutwardly of and surrounding said magnetized ring.
 3. A fan arrangementas defined in claim 2, said claw pole unit comprising a plurality ofradially outwardly projecting claw portions.
 4. A fan arrangement asdefined in claim 2, said claw pole unit comprising first and secondgroups of axially spaced peripherally offset radially outwardlyprojecting claw portions together defining a circumferential recess, andsaid pick-up winding means comprising electricaL wire means coiledaround said claw pole unit and accommodated in said circumferentialrecess.